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Paper 1

Transmon qubit readout fidelity at the threshold for quantum error correction without a quantum-limited amplifier

Chen L, Li H, Lu Y, Warren C, Križan C, Kosen S, Rommel M, Ahmed S, Osman A, Biznárová J, Roudsari AF, Lienhard B, Caputo M, Grigoras K, Grönberg L, Govenius J, Kockum A, Delsing P, Bylander J, Tancredi G.

Year
2022
Journal
Europe PMC
DOI
10.21203/rs.3.rs-1953331/v1
arXiv
-

No abstract.

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Paper 2

Fidelity-Guaranteed Entanglement Routing with Distributed Purification Planning

Anthony Gatti, Anoosha Fayyaz, Prashant Krishnamurthy, Kaushik P. Seshadreesan, Amy Babay

Year
2026
Journal
arXiv preprint
DOI
arXiv:2605.00246
arXiv
2605.00246

Many quantum-network applications require end-to-end Bell pairs whose fidelity exceeds a request-specific threshold, but existing entanglement routing algorithms either optimize only throughput without regard for fidelity or enforce fidelity guarantees using centralized controllers with global link-state knowledge. We present Q-GUARD, an online entanglement routing algorithm that enforces per-request fidelity thresholds within a distributed protocol model in which nodes exchange link-state information only with their $k$-hop neighbors. After link outcomes are realized in each slot, Q-GUARD builds per-link purification cost tables from realized Bell pairs, allocates per-hop fidelity targets using a Werner-state equal-split rule, and selects between candidate path segments using a segment-local expected-goodput (EXG) metric that jointly accounts for swap success, purification overhead, and resource availability. We also introduce Q-GUARD-WS, an extension that exploits per-link hardware quality estimates to allocate purification effort non-uniformly across hops. On synthetic 100-node topologies with heterogeneous link fidelity and stochastic BBPSSW purification, Q-GUARD raises the qualified success rate from under 20\% to over 85\% on 4-hop paths and nearly doubles the qualified service radius in Euclidean distance relative to throughput-only and naive-purification baselines, while Q-GUARD-WS provides additional throughput gains under high hardware heterogeneity.

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